Prostheses for implantation in blood vessels or other similar organs of the living body are, in general, well known in the medical art. For example, prosthetic endovascular grafts constructed of biocompatible materials have been employed to replace or bypass damaged or occluded natural blood vessels. Grafting procedures are also known for treating aneurysms. In general, endovascular grafts include a graft anchoring component that operates to hold a tubular graft component of a suitable graft material in its intended position within the blood vessel. Most commonly, the graft anchoring component is one or more radially compressible stents that are radially expanded in situ to anchor the tubular graft component to the wall of a blood vessel or anatomical conduit. In addition, the stents also have a patency function in that the stents keep the graft open and radially expanded along portions of the graft that are not necessarily opposed to the vessel wall, i.e., along portions of graft disposed within an aneurysm sac. Thus, endovascular grafts are typically held in place by mechanical engagement and friction due to the apposition forces provided by the radially expanded stents.
Stent-graft prostheses must be capable of withstanding the physiological dynamics that occur within the vessel or organ in which they are implanted. Thus, stent-graft prostheses must undergo testing to determine the fatigue limitations thereof. For example, the FDA currently requires medical device manufacturers of stent-graft prostheses to submit data to support the safety and efficacy of the permanent implant device. One required test data is the accelerated fatigue testing of stents or stent-graft prostheses. The FDA guidelines require ten years equivalent of test data, which translates to 400 million cycles of fatigue stress.
Devices for fatigue testers are usually hydraulic-based testing devices that force fluid within the lumen of a stent or stent-graft prosthesis in a pulsating fashion at a high frequency in order to simulate physiologic loading conditions, i.e., in order to simulate systolic and diastolic pressures. Such hydraulic-based testing devices operate at a maximum pulse frequency ranging between 1000-2000 cycles per minute, or approximately 16-33 Hz. In order to obtain the ten years equivalent of test data required by the FDA, such hydraulic-based testing devices must run continuously over a period of several months. Further, testing operation of such hydraulic-based devices must be closely monitored because pressure changes will change dilatation, thereby requiring the test to be restarted.
Hence, there is a need in the art for an improved fatigue tester that is configured to operate at higher frequencies for decreased testing times and/or that requires less monitoring during testing.